av8er50

My Feedback: (6)

I posted this on the battery page and haven't got a reply yet. I'll try here and hope someone will see it that has an answer for me.

Ok, I bought a Nelson on board glow driver from my LHS and when asked what battery to use he suggested a a JR 800 mah 4.8v nicad. Well after getting home I read the instructions for the glow driver and it says to use a 1.2v battery.
I don't understand how various batteries work and I want to make sure it wont cause the glow plug to fry. I am not concerned about the extra weight so I don't mind putting the 4.8v battery in, as a matter fact I would rather have a longer battery life if thats the way it works (I told you I am ignorant when it comes to batteries). Anyone that has any insight into this I would appreciate your help.

Thanks,

Jeff

trioval00

My Feedback: (17)

personaly, i would only use what the instructions say to use, i also have an onboard and i only use 1.2 volt and thats to lite a twin, doesnt need more battery then a 1.2


as always just my opionon

mark

WADE

My Feedback: (19)

Obviously, the guy at your LHS gave you wrong info. You want to use a 1.2V battery for the onboard since this voltage is what the glowplug needs. If you connect a 4.8V battery it will just blow the plug. Most people use a sub C rechargeable nicad battery for this purpose. If you want a longer life you can use a rechargeable D size battery, it will have a 1.2V output as well. Also, I don't see why a nimh battery wouldn't work fine. Hope this info helps.

Mike Denest

My Feedback: (1)

I use a single 1.2v 2000ma ni-cad on my OS .90 4 stroke. When I throw the switch, I can just about count the blades at idle. 1.2v is all you need.

KW_Counter

Can someone explain to me what the purpose of an onboard glow system is?
Thanks,
KW_Counter

av8er50

My Feedback: (6)

Thanks for all the info, it's kinda what I was thinking.
Now next question, if I cut the battery that I have down and just use one cell, then it is only a 1.2v, right. Again just wanna make sure I'm on the right page.

Jeff

trioval00

My Feedback: (17)

jeff912, yes if you cut the pack down you will still have 1.2 volts, each cell is 1.2, wilth only 1 cell you will have lower mah, but that will still fire your plugs,


KW COUNTER, there are many reason someone has an onboard glow system, first of many reasons would be easier starting, no need to attach your wire from power panel, 2 reason, and important one is better idle at low rpms. you can run a micro swith off of your throttle servo and at low throtle is will turn on the glow system. another reason old enya 4 strokes for example, have thier glow plug placed infront of the motor facing the prop, with on board you dont have to get your hand near the prop, last reason, it's just a neat toy / gadget to add to your aircraft

mark

av8er50

My Feedback: (6)

Mark,
On the picture supplied with my instructions it shows a single cell 1.2v (looks like a AA battery). Do you think it will work that way or maybe better with 2 cells?

KW Counter,
The reason I am using the onboard glow is to help the low idle. I am using a four stroke inverted, and they don't idle well inverted.

Jeff

Lightfoot

My Feedback: (1)

If you use 2 cells, they need to be in parallel so that you still have 1.2 volts but your load capacity is doubled. If you put them in series, you will have 2.4 volts with the same capacity.

av8er50

My Feedback: (6)

Is parallel with positive to positive and neg. to neg.? And series positve to neg. etc.
Also by doubling the load capacity does that extend the useable time?\

Jeff

Lightfoot

My Feedback: (1)

Yes to the parallel and series questions. Let's say that your glowplug draws 200 mA (I have no idea what the draw is for a glowplug) and your battery pack has a capacity of 800 mAh then it will last through 4 hours of draw, which is only during the time that the on-board glow driver is turned on. If the glow driver is only turned on for 10% of the time, then your total flying time with the battery pack would be 40 hours between charges.

av8er50

My Feedback: (6)

Lightfoot,

Is a regular batterpack parallel or in a series.
By regular I mean one used ie for a reciever. Is there a way of looking at the pack to see if it is parallel or series?
Jeff

BaronSchwab

Better be series.

Lightfoot

My Feedback: (1)

Receiver packs are made in series. With 4 - 1.2 volt cells in series, you get 4.8 volts. With 5 - 1.2 volt cells in series you get 6 volts. With 8 - 1.2 volt cells in series you get 9.6 volts like those used in tranmitters. Notice in the (crude) illustration that the batteries are straped positive (+) to negative (-). The wires are attached to the negative terminal of the battery on the left and the positive terminal of the battery on the right (the polarity of the image may be backwards). These batteries are in series, 1.2 volts per cell x 4 cells = 4.8 volts.

Think of it like this, voltage is the power that pushes the electricity (negatively charged particles) through wire. A battery cell could be thought of as a water pump of say 1.2 horsepower with a capacity of 200 gallons per minute. If you have 4 pumps in series, you would have 4.8 horsepower pushing the water through the pipe but the flow is still limited to 200 gallons per minute. If they are in parallel, you would have 1.2 horsepower pushing the water but each has a capacity to 200 gallons per minute so the flow would be 800 gallons per minute.

av8er50

My Feedback: (6)

Lightfoot,

That clears it up and helps make sense of it. I think I'll take the 4.8 volt battery back and get a 1.2 volt battery. That should save some $$$$. My other thought was put the 4.8 pack in a plane and trade out a rx pack for the new one. At any rate thanks for the detailed explanation, I appreciate the time you took to explain it.
Thanks again,
Jeff

F.Ciccarello

My Feedback: (60)

This is all good information. I like the micro switch method to turn the battery on or off.
If you can find a 2000 mah nicad battery that will work fine.